Patent GB-595941-A (GB)
Title: Improvements in or relating to the production of butyraldehyde
IPC: C07C45/62
Filed: 1945-07-10
Abstract: Apparatus for the catalytic hydrogenation of wet crotonaldehyde to butyraldehyde (see Group IV) comprises a glass tubular reactor 1, connected to a separator pot 3, a liquid circulating pump 4 and a cylindrical filter candle 5 enclosed in a jacket 6 forming an annulus 7.  A liquid reaction mixture comprising crotonaldehyde, butyraldehyde, water, n-butanol, a filter aid and nickel catalyst is continuously circulated by the pump through the filter candle, tubular reactor and separator pot, there being introduced into the system hydrogen at a point 8 and a mixture of wet crotonaldehyde and butanol at a point 15, a catalyst-free product being continuously <PICT:0595941/III/1> withdrawn at 16 and unused hydrogen removed at 18.  The catalyst collecting on the surface of the filter is washed off by the liquid mixture circulating through the annulus 7 and thereby maintained in suspension within the reaction system.ALSO:Butyraldehyde is prepared by the catalytic hydrogenation of crotonaldehyde in the liquid phase in the presence of a nickel catalyst by a process comprising hydrogenating wet crotonaldehyde at a temperature not in excess of 60 DEG  C., in the presence of an inert mutual solvent for water, crotonaldehyde and butyraldehyde, the wet crotonaldehyde containing more water than could be retained in the final liquid reaction mixture in the absence of the <PICT:0595941/IV/1> mutual solvent, said mutual solvent being present in an amount at least sufficient to maintain the liquid reaction mixture homogenous throughout the reaction.  The hydrogenation may be operated as a continuous process, by feeding hydrogen and the wet crotonaldehyde and inert mutual solvent continuously into a reactor, the latter two in such proportions that the liquid phase in the reactor comprises mainly butyraldehyde and remains homogeneous, and continuously withdrawing through a filter part of the liquid reaction mixture, substantially free from catalyst, at such a rate that the concentration of crotonaldehyde does not exceed 10 per cent by weight of the reaction mixture, the catalyst being maintained suspended in the liquid reaction mixture; advantageously, the wet crotonaldehyde and mutual solvent are fed continuously to a recirculating reaction system containing crotonaldehyde, butyraldehyde, water, a nickel catalyst and the mutual solvent in such proportions that the circulating reaction mixture remains substantially constant in composition and retains the water dissolved therein.  When the activity of the catalyst declines, the temperature may be raised to 80 DEG  C.  Preferably, the proportions of butyraldehyde to crotonaldehyde are at least 5 : 1 by weight.  Inert mutual solvents may be n-butanol and other alcohols, glycols, glycol-ethers and dioxane.  The process may be operated at ordinary or raised pressures.  Separation of catalyst from the reaction mixture may be effected by a filter, for example a filter candle, arranged in the reactor or in a continuous recycling system associated therewith in such a manner that the catalyst is continuously washed from the filter surface and thus kept suspended in the liquid mixture by the rapid movement of the latter over the filter surface.  An example illustrates a continuous recirculating process using the apparatus shown comprising a tubular reactor of glass 1, a separator pot 3 and a liquid circulating pump 4, there being situated between pump and reactor a filter candle 5 in a jacket 6 forming an annulus 7; the plant is charged with a mixture of 72 per cent butyraldehyde, 4.5 per cent crotonaldehyde, 15 per cent n-butanol and 8.5 per cent water and 3.8 parts Raney nickel catalyst modified by treatment with dilute acetic acid, and a little filter acid.  Hydrogen is passed into the system at 8 and a mixture of 76.5 per cent crotonaldehyde, 8.5 per cent water and 15 per cent n-butanol enters at a point 15 at such a rate that 95 per cent of the crotonaldehyde is converted; a catalyst free product is withdrawn continuously at 16 while unused hydrogen leaves at 18.  A yield of 94.5 per cent butyraldehyde is obtained. In the absence of the mutual solvent, the rate of hydrogenation falls to zero in a comparatively short time.  The Provisional Specification includes a reference to the continuous hydrogenation as above of crotonaldehyde, containing at least 4.35 per cent by weight of water. Specification 371,051, [Group III], U.S.A.  Specification 1,730,587 and German Specification 704,663 are referred to.